This sounds like a relaying issue to me but Vodafone have offered zero assistance. My father uses Spark for his mobile carrier (work phone) and operates a clear.net.nz personal email address. He is able to receive email from pop3.clear.net.nz while on the Spark network. He is intermittently able to send email via smtp.clear.net.nz but for the most part he can't.

Can anybody offer any advice to make this work? Webmail is not a viable solution.

Something I haven't tried is to use Sparks email server but I'm not sure they'd permit a ReplyTo address of clear.net.nz?

As to it working inconsistently on the mobile network, i have no known cases that would line up with this.

Normally paradise/Clear emails require a /p or something to access them off network.

In terms of a business explanation of the best steps here, we advise customers to go back to Clear (vodafone) to request for SSL STMP servers - This is a basic feature any mail system should offer at this stage...

Technically, this IS Vodafones issue to resolve as Port 25 filtering is pretty common (Vodafone do it themselves)

However, truth be told and as per your own findings Vodafone are not able to offer support for that. (in my previous role i would deal with 2-4 of these situations a week, well in the range of 50 when xtramail migrations first happened and security was tightened)

Spark Do have a work around available, however it is Unsupported.

If you have a Xtramail address, you can request verification added to that account for the clear account.

After that, you would setup your SMTP servers to sparks SSL servers and this should be good.

#include <std_disclaimer>

Any comments made are personal opinion and do not reflect directly on the position my current or past employers may have.

They simply need to set up SSL smtp access and offer a port other than 465

I don't necessarily agree with that 100% - you could just as easily argue the responsibility of providing SMTP lies with the RSP rather than the mail provider. Afterall you don't use a 3rd party DNS server because that is core infrastructure for a RSP as well. I'm not suggesting that all RSP's need to provide POP3 email, but many people need SMTP servers for various reasons.

At the end of the day IMHO SMTP/POP3 should be avoided at all costs for email as it's such a terrible solution and I don't understand why people still use it. With people wanting email of multiple devices these days anything that supports ActiveSync/EAS is still by far the best (and I'd argue only) solution for email.

When you can rock solid email with Activesync/EAS with your own domain as cheap as little as $10 or so per year I struggle to understand why people rely on their crippled RSP email services. Yes changing can be a pain, but that's short lived.